Dr. Ruth DeFries, Columbia University – The Earth From Above

In today’s Academic Minute, Dr. Ruth DeFries of Columbia University reveals what we can learn about how humans have altered the landscape when we view the Earth from above.

Ruth DeFries is Denning professor of sustainable development in Columbia University’s Department of Ecology, Evolution and Environmental Biology, and a faculty member of the university’s Earth Institute. Her research examines human transformation of the landscape and its consequences for climate, biogeochemical cycling and biodiversity. The research analyzes land use changes over broad scales through the lens of satellite observations, with a particular focus is tropical deforestation and its impacts on atmospheric carbon emissions and conservation.

Airline travelers glue their eyes to the window. Google Earth enthusiasts zoom from continent to continent from the comfort of their desks. We all have an urge to peer down on our planet--and recently it has become a lot easier, as the technology of satellite imagery has grown.

My own group’s research uses satellite data to see changes occurring across the tropics as people clear forests, cities expand and farmers grow more food in more places. What is emerging from this view? It reveals a rapidly transforming planet in the pursuit of more food and other products for a growing, and increasingly urban, population.

But at this point, the pace of these changes seems determined less by sheer population growth, and more by growing markets for biofuels, and prosperous city-dweller diets getting heavier all the time on meat and other animal products. These trends eat up tremendous amounts of land. Our analysis of satellite data shows that those tropical countries with the most forest loss were the ones with the most rapidly growing urban populations-- and the most international exports of farm products. Much like the European westward sweep across the prairies of North America in the 1800s, today agriculture is poised to transform many places across the tropics—but this time the technologies include tractors, fertilizers, and high-yield seed varieties rather than hoes, plows, and horses.

Certainly it’s a good thing that people have more food, and that economies can grow. But the health and environmental repercussions tell a troubling story. Tropical forests contain much of the planet’s natural machinery that recycles nutrients, stabilizes climate, and provides space and food for millions of species in addition to our own. The big challenge for this century is to use the ingenuity that has made us successful up to now to produce the food and other things we need without undermining the very life-support system on which we depend.